U.S. Pat. Nos. 3,815,416 and 4,924,703 assigned to the assignee of this patent application, disclose prior art apparatuses for indicating the level of liquid in a tank. The patented apparatuses comprise a float encircling the tube extending down into the tank. The float is magnetically coupled to a gauging rod which bears indicia representing the level of liquid in the tank. As the liquid level rises, the float carries the rod upwardly. The tankerman is apprised of the level in the tank by the visible indicia on the rod. Each patented apparatus also has a mechanism for automatically visually and audibly alerting the tankerman when the liquid has reached a particular level, such as near full.
The apparatus disclosed in these two patents is particularly suited for relatively shallow tanks, say on the order of about eight feet. In the case of deeper tanks, the longer rod protrudes more from the tank, which creates problems with overhead clearance and obstructions, susceptibility of rod bending or breaking from wind forces or inadvertent collision with other objects, and a weakening of the magnetic coupling due to the weight of the rod.